This invention relates generally to electronic musical instruments, and more particularly to electronic organs and the like, wherein a multi-frequency generator is used to generate a plurality of audio frequencies corresponding to the plurality of notes associated with various keys or foot pedals on a musical instrument. The keys or foot pedals are arranged to give either a single note tone or a chord note tone as desired.
Electronic organs have become relatively common in the musical industry and provide means for simulating the sounds produced by larger wind operated pipe organs, and the like. Such electronic organs differ from one another substantially in certain specific respects, such as whether the tone produced from the organ is obtained by a tone generator associated with additive or subtractive circuits. They also differ as to the specific type of generator used to obtain the base frequency, as for example, whether they are transistor or tube oscillators, wind-driven reed elements, rotating tone wheels and the like. However, all of these electronic organs can be distinguished by certain common features. In particular, each organ has a plurality of tone generators, there being one tone generator for each note of the keyboard and foot pedal associated with a two-manual type organ. Furthermore, associated with the least expensive types of electronic organs there is a single tone generator which is to be associated with the plurality of pedal tones, these tones being driven by one or more divider circuits connected to the single tone generator, which divides the frequency from the keyboard to obtain the desired notes. This is accomplished without difficulty because only a single pedal note is played at a time so that only a single generator is needed to produce the various signals.
It will be immediately apparent that there is a rather significant redundancy of tone generators used in prior art types of electronic organs. However, since the maximum number of notes that normally can be played at any one time is twelve, one note for each finger of the two hands and one note for each foot when manipulating the foot pedals, there are a multitude of tone generators that are not in use during this time. In popular organ playing, it is unusual to use more than one pedal tone at a given time and it is to be expected that no more than perhaps five notes will be played at any given time by the fingers of both hands. Some effort has been made to reduce the redundancy of tone generators needed by using tunable oscillators, wherein an oscillator is shared with two or three adjacent notes on the keyboard. This is done under the presumption that only one of these notes will be played at any given time. However, the presumption does not always hold true, and this is at best a low cost approach to developing electronic musical instruments of this type. In any event, there are still more tone generators needed than can be utilized at any one time by a single person playing with both hands and both feet.
The oscillators or other tone generator devices provide an audio frequency oscillation which bears a direct relation to the frequency of the note being played by the particular key on the keyboard or foot pedal. In the case subtractive of organ circuits, the note generated is the fundamental of the note played. In this case a large number of harmonics are provided by the particular generator, and the undesired harmonics are filtered out in accordance with the organ stop which is then being used. On the other hand, in the case of additive organ circuits, the tone generated may be a sub-harmonic of the tone played and the sub-harmonic is then multiplied to achieve the desired audio-frequency output.
All of the electronic organ circuitry heretofore utilized have been of the type which require discrete active and passive components formed in relatively large chassis or secured to large circuit boards or the like. These large circuit boards generally may be of the printed circuit type formed on fiberglass or other non-conductive sheet material. These discrete components may take the form of individual tubes or transistors as well as including a multitude of inductance and capacitance elements which provide the necessary LC circuits for the oscillators. Furthermore, coupling capacitors and voltage developing resistors may be included in the plurality of discrete electronic components. This type of prior art configuration, and any of the above types of organ arrangements, is relatively complex to manufacture, and furthermore, requires a substantial amount of maintenance over the life of the organ. As well as corrective and preventative maintenance, occasional tuning of the oscillator circuits is required to maintain the organ tone qualities in tune.